1. Field of the Invention
The present invention relates to the recovery of granulocytes from human blood by a procedure which is commonly known as filtration leukapheresis. The isolated granulocytes are transfused into patients who have a low white cell count (neutropenia), and therefore are at increased risk to infection, are infected, or are not responding to antibiotics. This type of granulocyte support has been used clinically for more than 15 years. Recently, with the increase use of chemotherapy in the treatment of cancer, the need for white cell therapy has risen sharply because the drugs used also reduce the capacity of the bone marrow to produce granulocytes.
2. State of the Prior Art
Human blood is usually separated into various cellular components and plasma by centrifugation. However, centrifugal techniques for isolation of granulocytes requires expensive equipment and usually demand a high level of skill on the part of the operator of the centrifuge. For this reason, the simpler approach of filtration leukapheresis has important advantages for separation of granulocytes. The present commercial filtration leukapheresis system utilizes a cylindrical container (pack) filled tightly with short lengths (1.5") of nylon fiber. Generally when anti-coagulated whole blood is passed through the pack a portion of the granulocytes and some mononuclear cells adhere to the nylon fiber packing. The granulocytes are subsequently eluted from the packed fiber column by backwashing the column with a solution containing a chelating agent. In order to further facilitate elution of cells from the column, the pack is also tapped vigorously. This type of pack is disclosed in U.S. Pat. No. 3,462,361.